Rooster or hen?

We bought several chicks this spring at the local feed store, all were supposed to be hens. They are now about 20 weeks or so. We had a rooster before these chicks, and the main flock stays with him. I'd say like 14 hens hang with the older rooster. This chicken hangs out in a smaller flock of 4 hens, is larger than the others of same breed and age, and has been seen mounting them. But there are no spurs, and no crowing. Is this a rooster also (the dark, reddish one)? We have plenty of space for another rooster, and if it is a hen, well, we accept her for what she is.

Brahmas are slower to mature, they often don't crow until closer to a year old. Plus, they're pretty docile and tend to yield to an older roo of a different breed, from what I've seen folks post here. So, the presence of the older roo may keep your boy from crowing for quite a while.